This invention relates to a method and apparatus for air cooling of integrated circuit computer chips and more particularly to a method and apparatus for air cooling an array of such chips by utilization of an air-cooled evaporator and condenser apparatus, the evaporator and condenser being self-contained and requiring no external power source.
With high power computers of modern design, there is a need to meet market demands for air-cooling of such high power computer systems. Attempts to use air to cool extremely high powered semiconductor devices or chips have proven inefficient, since air is not a highly efficient heat transfer medium. Heat transfer from a high powered chip to an air cooled system requires a very large heat dissipation area or heat sink. Modern chip packaging techniques, which allow for the housing of several high powered chips in a very compact area, creates the problem of requiring a large heat sink area for heat dissipation.
Attempts have been made to use liquid cooling as a means of cooling high powered chips. However, liquid cooling requires pumps and tubing, and, in most instances, an additional cabinet to accommodate this type of cooling. In addition, customers for such computers exhibit low confidence in liquid cooling.
One such attempt at liquid cooling for electronic components is direct immersion ebullient heat transfer, whereby the semiconductor components are totally immersed within a dielectric liquid. The degree of cooling depends on finding a dielectric liquid with suitable phase-change and dielectric characteristics. Another immersed component cooling system traditionally utilizes a finned condenser coil within the vapor space for heat removal. Condensers for such ebullient systems can be located in the vapor space above the components or located remotely.
Other systems, such as the Cray 2 computer, utilize a forced convection direct immersion system which does not boil. The liquid flows past the components, where it picks up heat and then flows to an external heat exchanger where it is cooled. The fluid flow in this system requires pumps and external tubing.
With systems having the integrated circuit chips immersed in a coolant or boilable liquid, care must be taken in selection of the liquid, that is, the dielectric and corrosive properties of the liquid, along with the heat transfer characteristics and vapor phase change temperature, must be considered in providing a highly reliable cooling system.
Other systems have employed conventional finned heat sink structures, in an air-cooled arrangement, but such systems are usable only for low power dissipation devices. Since air is not a very efficient cooling medium, the amount of heat removed is low. Thus, unless a higher air contact area is provided, this approach is suitable only for relatively low powered chips.
In accordance with an aspect of the invention, a multi-chip module is provided with a self-contained mechanically attachable cooling unit.